1. Field of the Invention
The present invention relates to a powder-compacting method and apparatus suited for a process in which powder (hereinafter simply called powder, which includes granulated powder containing a binder) is compacted in a manufacturing line, such as ceramics, powder metallurgy, a magnetic material in the field of electric materials, a ferrite magnet, and a rare earth magnet. More particularly, it relates to a powder-compacting technique and apparatus in which the apparatus includes a mechanism designed to sequentially apply a sufficient pressure for the powder compacting to each part of a pressurized area, while the technique includes step compression for reducing a total pressurizing force.
2. Description of the Related Art
It has heretofore been believed that powder compacting usually requires a total pressurizing force in which a sufficient pressure to obtain a target compacting density is applied to the entire compact or an area (an area of a die opening) in a direction in which the pressure is projected.
A mold for use in the powder compacting includes a die and upper-lower punches when a compact does not includes a hole in a direction in which pressure is applied. The mold is filled with powder, which is then pressurized by the upper-lower punches. The total pressurizing force is applied to an area of the powder at which the punches contact the powder.
A compact positioned in the middle of the mold after pressurization is knocked out and then thrown out of the mold by means of the lower punch. In the process of such an operation, the compact is held in frictional contact with an inner wall surface of the die under elevated pressure. As a result, a high level of discharging pressure is required during knockout. In metallic powder, there occur defects during a series of the above processes, such as scuffing adhesion between the inner wall of the die and the punches, cracks, and chip-off. In addition, other general compacts such as oxides tend to chip off, crack, and laminated-crack because of internal distortion.
In order to eliminate such defects, the die is made of an ultra-hardened alloy having good abrasion resistance to the powder, or otherwise a special film having a reduced degree of surface adhesion is applied to the die. In addition, a mold for the die must be fabricated with a high degree of precision.
It is assumed that a basic patent on the above powder compacting was initially filed in Europe nearly at the year of 1910. (See xe2x80x9cHistory and Development of Powder Metallurgyxe2x80x9d by Kimura Hisashi, issued by Agune Gijyutu Center.)
A powder compacting process under magnetic field conditions in the field of magnets is described in, e.g., xe2x80x9cMagnetic Materials for New Eraxe2x80x9d issued by Mitokako Kakoh Gijyutu Kyoukai, second edition, 1983, and xe2x80x9cCOBALT 53xe2x80x9d, December 1971, by R. E. Johnson, A. I. M., and C. J. Fellows, on pages 191-196. In addition, the same powder compacting process has recently been filed for patent, as seen from published Japanese Patent Application Laid-Open No.3-40861.
However, similarly to the above-mentioned typical powder compacting, the prior art as given above pressurizes the die at a pressurized opening area thereof, and thus requires a similar total pressurizing force.
In an overall process for manufacturing a product in each field, a compacting process is believed to require the most important key technology that determines manufacturing cost of the product as well as a quality level of the product. The present invention provides a new key technology-based technique and apparatus to related wide fields.
The prior art powder compacting as described above has shortcomings of high energy to be supplied to an apparatus, high costs, and a large-scaled apparatus with a consequential increase in space to be occupied by such an apparatus, because a large-sized powder compact, an elongated powder compact, a plurality of powder compacts are produced by a large-scaled compacting apparatus having an increased overall pressurizing force.
In view of the above, an object of the present invention is to provide an improved powder-compacting method and apparatus designed to require a reduced level of a pressurizing force for powder compacting, thereby allowing powder to be compacted by means of a smaller-scaled compacting apparatus instead of a larger-scaled compacting apparatus.
A powder-compacting method according to the present invention comprises the steps of: filling powder to be pressurized into a molding container; and, individually pressing a plurality of pressurizing members in sequence toward the powder, the pressurizing members being aligned on a pressurized surface of the powder through an elastic plate.
According to the present invention, step compaction makes it possible to reduce a total pressurizing force required for conventional techniques, and thus allows a smaller-scaled compacting apparatus to compact the powder. As a result, a low cost apparatus is achievable.
A powder-compacting apparatus according to an aspect of the present invention comprises a molding container having a plurality of pressurizing members disposed on a bottom of the container, and further having an elastic plate disposed on the pressurizing members as a bottom surface, wherein the plurality of pressurizing members are sequentially driven to pressurize powder via the elastic plate for compacting.
A powder-compacting apparatus according to another aspect of the present invention comprises: a molding container having a bottom, the container having a powder-filled opening formed at an upper portion thereof and a wedge-inserted hole defined through a sidewall of the container; a plurality of pressurizing members aligned on a bottom plate of the molding container; an elastic plate disposed on the plurality of pressurizing members for providing a bottom surface of the powder when the powder is filled into the molding container through the powder-filled opening; a lid body for closing the powder-filled opening; and, a wedge inserted into the molding container through the wedge-inserted hole, the wedge being pushed along the bottom plate into between an inner surface of the bottom plate and the pressurizing members, thereby permitting the plurality of pressurizing members to sequentially pressurize the powder via the elastic plate for compacting.
In a powder-compacting apparatus as previously defined, at least the lid body and compacting surfaces of the pressurizing members contiguous with the elastic plate are curvilinear in shape in order to allow the compact to be formed into one of a pillar shape, substantially semi-pillar shape, substantially semi-cylindrical shape, partially cylindrical shape.
The above structure provides compacts having a wide variety of shapes.
In a powder-compacting apparatus as previously defined, the wedge includes a slanted surface for raising the pressurizing members and a planar surface continuously extending from the slanted surface for retaining the pressurizing members at a position where the pressurizing members are raised.
The above structure allows the powder to remain pressurized for a certain time. This feature prevents the occurrence of cracks in the compact.
In a powder-compacting apparatus as previously defined, the molding container has an inner peripheral surface tapered at the powder-filled opening so as to expand outward.
The above structure permits a knockout position at which the compact is discharged to be positioned adjacent to an opening of the container at the top of the die. In addition, the draft-tapered upper opening reduces a draft pressure and internal compact distortion. Such a reduction in internal compact distortion contributes toward reductions in compact chip-off, cracks, and laminated cracks, eliminates an inconvenience of scuffing on a die, which otherwise would occur in metallic powder. Moreover, the reduced internal compact distortion is believed to contribute toward reductions in quantity of binders and lubricating agents, which are required for various kinds of powder. Furthermore, in conventional techniques, the die must involve an expensive ultra-hardened alloy, a mold structure sufficient to withstand high pressure, and specific dimensional precision, with which the compact is fabricated. Meanwhile, the present invention is free from such requirements, and can employ an inexpensive mold structure.
In a powder-compacting apparatus as previously defined, the upper lid serves as a magnetic field yoke, the magnetic field yoke having a coil wound therearound in order to vertically generate a magnetic field in the molding container.
The above structure provides a simply structured magnetic field-applying apparatus.
In a powder-compacting apparatus as previously defined, a coil is trained around the molding container in order to generate a magnetic field in the molding container in a direction in which the wedge is advanced and retracted.
Such a structure provides a simply structured magnetic field-applying apparatus.
In a powder-compacting apparatus as previously defined, the molding container includes one of a plurality of the same compacting sections and a plurality of different compacting sections, and the wedge, elastic plate, and pressurizing members are provided so as to correspond with the compacting sections, the wedge having a proximal end combined together.
Such a construction further facilitates realizing a smaller-scaled apparatus.
In a powder-compacting apparatus as previously defined, the wedge has the slanted surface and the planar surface continuously extending therebetween in a stepwise manner so as to form a several stage construction.
Such a construction allows the wedge to be driven in stages, and thus allows a driving apparatus to provide a reduced level of a driving force.
In a powder-compacting apparatus as previously defined, the molding container includes a core for forming a hollow in the compact, and the pressurizing members and the wedge are both configured to avoid the core.
In a powder-compacting apparatus as previously defined, the lid body is provided with a slicer that protrudes into the molding container for dividing a compact during powder compacting.
Such a construction makes it possible to produce a plurality of compacts at one time.
In a powder-compacting apparatus as previously defined, the pressurizing member includes a plurality of concentric cylinders, the wedge including a V-shaped pointed end, the wedge having a plurality of slanted surfaces formed along an inner surface of the V-shaped pointed end for sequentially raising the pressurizing members.
In a powder-compacting apparatus as previously defined, the pressurizing member is defined with a convex surface at an upper end thereof, while the elastic member is formed with a concave surface to be engaged with the convex surface of the pressurizing member.
Such a construction alleviates a tensile force of the elastic plate.
A powder-compacting apparatus as previously defined further comprises: an upper lid-lifting apparatus for raising and lowering an upper lid for closing an upper opening of the molding container; a discharging apparatus spaced apart from the upper lid-lifting apparatus for discharging a compact out of the molding container; a delivering means for reciprocably delivering the molding container between the upper lid-lifting apparatus and the discharging apparatus; a filling apparatus disposed between the upper lid-lifting apparatus and the discharging apparatus for filling the next pack of powder to be compacted into the molding container through the upper opening of the molding container after the discharging apparatus discharges the compact out of the molding container; and, a wedge-driving means for permitting a wedge for sequentially driving the pressurizing members to be inserted into the molding container after the upper lid-lifting apparatus closes the upper opening of the molding container.
Such a construction provides a simplified structure of the entire apparatus.
In a powder-compacting apparatus as previously defined, the wedge-driving means moves the wedge in a direction identical to a direction in which the molding container is moved.
Such a construction allows all of the apparatus to be aligned on a line, and a simplified space is available.
A powder-compacting apparatus as previously defined further comprises: a driving apparatus including an upper lid for closing an upper opening of the molding container and a powder-filling apparatus for filling powder into the molding container through the upper opening, the driving apparatus permitting a combination of the upper lid and the powder-filling apparatus to be individually moved to a position above the upper opening; a wedge-driving apparatus including a wedge inserted between the pressurizing members and a bottom of the molding container for permitting the pressurizing members to pressurize the powder via the elastic plate, the wedge-driving means designed to insert and retract the wedge; and, a discharging apparatus for raising the bottom of the molding container to discharge a compact out of the molding container through the upper opening after the wedge is pulled out of the molding container, the bottom of the molding container being free to rise and lower, wherein the driving means permits a pointed end of the upper lid to push the compact to a position where a product is discharged, while causing the powder-filling apparatus to be positioned above the upper opening.
In a powder-compacting apparatus as previously defined, the wedge includes a plurality of laminated components, each of which is individually driven by a driving means.
Such a construction is able to drive the wedges with a reduced level of a driving force.
A powder-compacting apparatus as previously defined further comprises: a magnetic field coil, in which the molding container is inserted; an upper lid attachment-detachment apparatus disposed adjacent to the magnetic field coil for attaching and detaching an upper lid that closes an upper opening of the molding container; a discharging apparatus disposed on the side opposite to the upper lid attachment-detachment apparatus for discharging a compact out of the molding container; a delivering means for reciprocably delivering the molding container between the magnetic field coil and the discharging apparatus; a filling apparatus disposed between the upper lid attachment-detachment apparatus and the discharging apparatus for filling the next pack of powder to be compacted into the molding container through the upper opening of the molding container after the discharging apparatus discharges the compact out of the molding container; and, a wedge-driving means disposed on the side opposite to the upper lid attachment-detachment apparatus, the wedge-driving means including a wedge for sequentially driving the pressurizing members while the upper lid attachment-detachment apparatus closes the opening of the molding container and the molding container is positioned in the magnetic field coil, the wedge-driving means being designed to insert the wedge into the molding container.
In a powder-compacting apparatus as previously defined, the powder-compacting apparatus are aligned longitudinally and transversely, and the powder-compacting apparatus share a common material powder tank.
Such a construction allows for further downsizing of the apparatus.
In a powder-compacting apparatus as previously defined, inert gases are hermetically sealed up within the powder-compacting apparatus.
Such a construction facilitates preventing oxidation of rare earth magnet powder, and thus expects magnetic characteristics that involve a higher level of performance. In addition, a reduced amount of inert gases can be sealed with ease.